We have investigated the effects of acute alcohol intoxication and age on aircraft pilots' simulated flight performances for several years with the objective of better understanding the acute and hangover effects of alcohol on aviation ability. Current Federal Aviation Administration (FAA) regulations permit pilots to fly eight hours after drinking if the blood alcohol concentration (BAC) is less than 0.04%. However, we have observed that some pilots are impaired in a hangover condition eight hours after drinking and other research groups have observed impairment at BACs as low as 0.04%. Our previous studies have found that both acute and hangover alcohol effects include significantly increased variability of performance of pilots relative to placebo conditions, which suggests individual differences in susceptibility to alcohol impairment. The overall goal of our proposed research is to determine what makes some pilots more susceptible than others. We will investigate the roles that speed of processing, age, practice, gender, and ethnic/racial group play in pilots' susceptibility to the effects of alcohol. We have found that baseline performance on computerized measures of speed of information processing predicts degree of acute alcohol impairment, but does not predict hangover effects. In our proposed work we will refine our predictive and dependent measures with the aim of better identifying which individuals will experience hangover effects in simulated flight. We plan to test the hypothesis that baseline performance on speed of processing tasks is a crucial mediator of pilot's susceptibility to acute and hangover alcohol effects. Some but not all studies of age, alcohol, and pilot performance have observed older pilots to be more susceptible to alcohol impairment. Based on findings that speed of processing declines with age, we propose to test the hypothesis that observed age differences in susceptibility to alcohol can be largely accounted for by differences in processing speed rather than age alone. In all our studies, increased practice on flying tasks apparently attenuated the deleterious effects of hangover. We plan to study systematically how the amount of practice, both with alcohol and without, affects the decrement in performance. Overall, we expect that degree of practice will modulate the roles that age and alcohol play in performance. Specifically, we hypothesize that increasing amounts of practice should attenuate the overall detrimental effects of both age and alcohol on pilot performance. The issues of processing speed, age and practiCe will be addressed jointly in a parallel groups design where amount of pre-drug and on-drug practice are crossed factorially and where subjects span an age range of 21 to 70 years. There will be 150 subjects in these studies. We will also address gender and ethnic differences in separate studies each involving 30 subjects.